In today's wireless communication networks, user devices such as electronic book readers, cellular telephones, personal digital assistants (PDAs), portable media players, tablet computers and netbooks typically have to search for cells when they are powered on. A cell belongs to a public land mobile network (PLMN) that provides land mobile telecommunications service to user devices. Generally, each service provider operates its own PLMN.
When a user device is powered on, the user device typically first looks for a PLMN on which the user device was last registered in the frequency band of a cell on which the user device was previously camped. If the last registered PLMN is not found in this frequency band, the user device searches for the last registered PLMN in other frequency bands supported by this PLMN. If that search is unsuccessful or there is no history of the last registered PLMN, the user device searches for the home or higher priority PLMN in frequency bands supported by the home PLMN. If the home or higher priority PLMN is not found, the user device searches on all frequency bands supported by the user device, and selects a PLMN that has the highest priority in a PLMN list on the SIM card or non-volatile memory of the user device.
The above procedure works well when a user device is powered on in an area serviced by its last registered PLMN or its home PLMN. However, when a user device is powered on at a location where the last registered PLMN or home PLMN are not available, the above procedure causes a significant delay in acquiring wireless service by the user device because the user device has to exhaust its search for the last registered and home PLMN before camping on a new PLMN.